Treatment of sleep disordered breathing (SDB), such as obstructive sleep apnea (OSA), by continuous positive airway pressure (CPAP) mask systems involves the continuous delivery of air (or other breathable gas) pressurized above atmospheric pressure to the airways of a human or other mammalian patient via a conduit and a mask. Typically, the mask fits over the nose and/or mouth of the patient. Pressurized air flows to the mask and to the airways of the patient via the nose and/or mouth. As the patient exhales, carbon dioxide gas may collect in the mask. A washout vent in the mask or conduit discharges the exhaled gas from the mask atmosphere.
When nasal mask systems are used, e.g., nasal masks or nozzle assemblies, some patients have a tendency for mouth leak. Alternatively, some patients may have a tendency for mouth breathing when using a nasal mask system. When air escapes through the patient's mouth, the patient does not obtain the full benefit of the delivered treatment pressure. Therefore, the effectiveness of CPAP therapy is diminished. In addition, mouth leak may result in noise, increased treatment pressure to compensate for the leak, increased load on the nasal passages, nasal obstruction, and/or runny nose, for example. The reduction of mouth leak and the prevention of mouth breathing encourage nasal breathing which may prove beneficial for the patient.
PCT Application No. PCT/AU2004/001832 and U.S. Pat. Nos. 1,873,160, 5,560,354, 6,123,082, and 6,571,798 disclose devices that attempt to reduce mouth leak.